1. Field of the Invention
The present invention relates generally to wet-dye, hard copy apparatus, more particularly to staggered pen arrangements in ink-jet printers, and more specifically to a method of improved throughput printing, including simultaneous printing on multiple pages.
2. Description of Related Art
The art of wet-dye printing--such as with ink-jet technology, liquid toner laser technology, and the like--is relatively well developed. For example, commercial ink-jet products such as computer printers, graphics plotters, copiers, and facsimile machines employ ink-jet technology for producing hard copy. The basics of jet-ink technology are disclosed, for example, in various articles in the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1995), Vol. 39, No. 4 (August 1988), Vol. 39, No. 5 (October 1988), Vol. 43, No. 4(August 1992), Vol. 43, No. 6 (December 1992) and Vol. 45, No. 1 (February 1994) editions. Ink-jet devices are also described by W. J. Lloyd and H. T. Taub in Output Hardcopy [sic] Devices, chapter 13 (Ed. R. C. Durbeck and S. Sherr, Academic Press, San Diego, 1988).
In U.S. Pat. No. 5,376,958 (assigned to the common assignee of the present invention and incorporated herein by reference) for Staggered Pens in Color Thermal Ink-Jet Printer to Brent Richtsmeier et al. (hereinafter "Richtsmeier"), a color ink-jet printer includes a print carriage movable along a carriage scan axis and a plurality of color producing ink-jet printheads supported by the print carriage and offset relative to each other so that their nozzle arrays are non-overlapping along the media scan axis (perpendicular to the carriage scan axis). The nozzle arrays of the ink-jet printheads traverse no-overlapping regions as the carriage is scanned along the carriage an axis. The construct thus provides for drying of ink drops prior to application of any overlying ink drops.
Generally, the pen scanning axis is referred to as the x-axis, the print media transport axis is referred to as the y-axis, and the ink drop firing direction is referred to as the z-axis. See e.g., FIGS. 1-3.
It is a perennial goal of hard copy apparatus designers to increase throughput, an important consideration for the end-user. Thus, among hard copy apparatus original equipment manufacturers, the design criteria is "faster is better." For scanning carriage ink-jet technology, the goal is to try to match the substantially faster page-per-minute "ppm" capability in state-of-the-art electrostatic and laser printing technology.
In thermal ink-jet technology, the use of thin-film and semiconductor technology to produce printheads has permitted the nozzle density to increase. In other words, where only a few years ago Hewlett-Packard.TM. DeskJet.TM. Stanley-model printheads had a nozzle array height of about one-sixth inch with nozzles separated by 1/180.sup.th -inch, the state of the art has progressed to where nozzle arrays of one or more inches in height with hundreds of nozzles separated by only 1/600.sup.th -inch. It can thus be recognized that in a standard ink-jet scanning printer, throughput efficiency is degraded with the larger printheads because many nozzles will not be firing as swaths are created along leading and trailing edges of the print media, namely, when part of the printhead is hanging over the edge of the page.